Science: The Frontier of Space

The best-known wind tunnels are vast, bellowing monsters that soak up
the local power supply and drive the neighbors nuts. Last week Dr.
Richard G. Folsom of the University of California described a quieter
and trickier tunnel. Built with Navy and Air Force funds, it is a
stainless steel tube only 5 ft. long and 18 in. in diameter. Its
purpose: to simulate aerodynamic conditions near the earth's outer
frontierthe atmosphere 50 miles up.

At this altitude and above, the air is so thin that it does not act as a
normal gas. Its molecules are in motion, but instead of colliding...